Processes for producing phenoxy propionic acid derivatives

ABSTRACT

The present invention relates to processes for producing D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid and ester derivatives thereof and which can be used as selective herbicides for foliage treatment for controlling gramineous weeds against broad leaf crop plants.

This application is a 371 of PCT/JP97/01711, filed May 21, 1997.

TECHNICAL FIELD

The present invention relates to processes for producingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid andD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid estersderived from the propionic acid. The esters are useful as selectiveherbicides for foliage treatment for controlling gramineous weedsagainst broad leaf crop plants.

BACKGROUND ART

Nippon Kagaku Kaishi, p. 253, (1991) discloses a process for producingethyl D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, whichcomprises reacting an alkali metal salt of4-(6-chloro-2-quinoxalyloxy)phenol with ethyl L-2-chloropropionate.JP-A-7-278047 discloses a process for producingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, whichcomprises reacting an alkali metal salt and/or an alkaline earth metalsalt of 4-(6-chloro-2-quinozalyloxy)phenol with an alkaline earth metalsalt of L-2-chloropropionic acid. Further, U.S. Pat. No. 4,687,849discloses a process for producing 2-isopropylidene aminoxyethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting 2-isopropylidene aminoxyethylL(-)-2-(p-toluenesulfonyl)oxypropionate with4-(6-chloro-2-quinoxalyloxy)phenol, a process for producing2-isopropylidene aminoxyethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting 2-isopropylidene aminoxyethylD(+)-2-(4-hydroxyphenoxy)propionate with 2,6-dichloroquinoxaline, and aprocess for producing 2-isopropylidene aminoxyethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidchloride with 2-isopropylidene aminoxyethanol. Further, JP-B-7-25753discloses a process for producing tetrahydrofurfuryl2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting tetrahydrofurfuryl 2-bromopropionate with2-(4-hydroxyphenoxy)-6-chloroquinoxaline, and JP-A-4-295469 discloses aprocess for producing 2-isopropylidene aminoxyethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesan ester exchange reaction of ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate obtained by areaction of 2,6-dichloroquinoxaline with ethylD(+)-2-(4-hydroxypheoxy)propionate.

The process disclosed in Nippon Kagaku Kaishi, p. 253 (1991) is notnecessarily industrially satisfactory for producing a product of highoptical purity.

Whereas, JP-A-7-278047 discloses that in the reaction of an alkali metalsalt of 4-(6-chloro-2-quinoxalyloxy)phenol with an alkali metal salt ofL-2-chloropropionic acid, the reaction is terminated at a conversion ofabout 50% due to a side-reaction, and the yield is very low. The samepublication also discloses that a barium salt is particularly preferredas the alkali salt and/or the alkaline earth metal salt. However, if thebarium salt is used, there is a problem that a large amount ofbarium-related compounds as typical by-products is formed, and it hasbeen desired to develop a more efficient production process.

DISCLOSURE OF THE INVENTION

The present inventors have conducted an extensive study to solve theabove-mentioned problems and as a result, have accomplished the presentinvention. Namely, the present invention provides a process forproducing D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid(hereinafter referred to as compound (III)), which comprises reacting4-(6-chloro-2-quinoxalyloxy)phenol (hereinafter referred to as compound(I)) or its alkali metal salt with L-2-chloropropionic acid (hereinafterreferred to as compound (II)) or its alkali metal salt in an aromatichydrocarbon solvent in the presence of an aprotic polar solvent and, ifnecessary, an alkali metal hydroxide, if necessary while carrying outazeotropic dehydration, to obtain an alkali metal salt ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, and treatingit with an acid.

By the process of the present invention, compound (III) can be producedat a high conversion in good yield without deterioration of the opticalpurity.

Further, in the process of the present invention, an alkali metal saltof D-2-chloropropionic acid may be employed instead of the alkali metalsalt of L-2-chloropropionic acid to obtainL(-)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, which can beinverted to produceD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid.

Further, compound (III) produced by the process of the present inventioncan be esterified to produce a heteroaryloxy propionic acid typeherbicide, such as ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate,tetrahydrofurfurylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, orisopropylidene aminoxyethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate.

For example, it is possible to produce ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate by reactingcompound (III) with diethyl sulfate in the presence of a tertiary amineand a base.

The present invention is also useful for producing other heteroaryloxypropionic acid type herbicides such as fluazifop-p-butyl (common name)and fenoxaprop-p-ethyl (common name).

Now, the present invention will be described in detail with reference tothe preferred embodiments.

The alkali metal salt of compound (I) may, for example, be a potassiumsalt or a sodium salt.

The alkali metal salt of compound (I) can be produced from compound (I)and an alkali metal compound.

The alkali metal compound may, for example, be a metal such as sodium orpotassium, an alkali metal hydride such as sodium hydride or potassiumhydride, or an alkali metal hydroxide such as sodium hydroxide orpotassium hydroxide. In view of the reactivity and economicalefficiency, sodium hydroxide is preferred.

The amount of the alkali metal compound is usually within a range offrom 1 to 10 mols, preferably from 1 to 2 mols, per mol of compound (I).

Further, the alkali metal salt of compound (I) can also be prepared from2,6-dichloroquinoxaline (hereinafter referred to as compound (IV)),hydroquinone and an alkali metal compound.

The alkali metal compound may, for example, be a metal such as sodium orpotassium, an alkali metal hydride such as sodium hydride or potassiumhydride, or an alkali metal hydroxide such as sodium hydroxide orpotassium hydroxide. In view of the reactivity and economicalefficiency, sodium hydroxide is preferred.

With respect to the amount of the alkali metal compound, for example, inthe case of sodium hydroxide, the amount is usually within a range offrom 1.8 to 3 mols, preferably from 2.0 to 2.5 mols, per mol of compound(IV).

The amount of hydroquinone is usually within a range of from 1 to 1.5mols, preferably from 1.00 to 1.05 mols, per mol of compound (IV).

For the production of compound (I) or its alkali metal salt, an organicsolvent may also be used, as the case requires. The organic solvent ispreferably an aprotic polar solvent, more preferablyN,N-dimethylformamide. Further, a solvent mixture ofN,N-dimethylformamide with an aromatic hydrocarbon such as benzene ortoluene, may also be employed.

The reaction temperature is usually within a range of from 20 to 120°C., preferably from 50 to 70° C.

When water is formed during the production of the alkali metal salt ofcompound (I), formed water may be removed so that the reaction proceedssmoothly.

The alkali metal salt of compound (II) may, for example, be a potassiumsalt or a sodium salt.

The alkali metal salt of compound (II) can be produced from compound(II) and an alkali metal compound.

The alkali metal compound may, for example, be a metal such as sodium orpotassium, an alkali metal hydride such as sodium hydride or potassiumhydride, an alkali metal hydroxide such as sodium hydroxide or potassiumhydroxide, an alkali metal carbonate such as sodium carbonate orpotassium carbonate, or an alkali metal hydrogencarbonate such as sodiumhydrogencarbonate or potassium hydrogencarbonate. In view of thereactivity and economical efficiency, sodium carbonate is preferred.

The amount of the alkali metal compound is usually within a range offrom 1 to 10 mols, preferably from 1 to 2 mols, per mol of compound(II).

For the production of the alkali metal salt of compound (II), an organicsolvent may be used, as the case requires. The organic solvent is notparticularly limited so long as it is inert to the reaction. Forexample, an aromatic hydrocarbon solvent such as benzene or toluene ispreferred.

The reaction temperature is usually within a range of from 20 to 120°C., preferably from 50 to 70° C.

When water is formed during the production of the alkali metal salt ofcompound (II), formed water may be removed so that the reaction proceedssmoothly.

The method for reacting the alkali metal salt of compound (I) with thealkali metal salt of compound (II) may, for example, be a method inwhich the alkali metal salt of compound (I) and the alkali metal salt ofcompound (II) are separately produced and reacted, a method wherein thecompound (I) is reacted with compound (II) in the presence of an alkalimetal compound, or a method wherein the alkali metal salt of compound(I) is reacted with compound (II) in the presence of an alkali metalcompound.

Otherwise, it is possible to employ a method of adding the alkali metalsalt of compound (II) to the reaction solution at the time of theproduction of the alkali metal salt of compound (I), or adding an alkalimetal hydroxide and compound (II) to the reaction solution at the timeof the production of the alkali metal salt of compound (I).

The amount of compound (II) or its alkali metal salt is usually within arange of from 1 to 1.5 mols, preferably from 1.1 to 1.3 mols, per mol ofcompound (I) or its alkali metal salt.

The solvent to be used for the reaction of compound (I) or its alkalimetal salt with compound (II) or its alkali metal salt, is preferably anaromatic hydrocarbon solvent containing an aprotic polar solvent. Theaprotic polar solvent may, for example, be N,N-dimethylformamide,N,N-dimethylacetamide, N-methylpyrrolidone or1,3-dimethyl-2-imidazolidinone. Particularly preferred isN,N-dimethylformamide. The aromatic hydrocarbon solvent may, forexample, be toluene or benzene, and particularly preferred is toluene.Further, a solvent mixture of the above-mentioned solvents used for theproduction of the respective compounds, may also be used.

The organic solvent may be used in a large amount without any particularproblem. However, taking the economical efficiency and the reactivityinto consideration, it is preferably used in an amount of from 8 to 9parts by weight per part by weight of compound (I).

The reaction temperature is usually within a range of from 20 to 120°C., preferably from 50 to 70° C.

When water is formed in the reaction of compound (I) or its alkali metalsalt with compound (II) or its alkali metal salt, formed water may beremoved so that the reaction proceeds smoothly.

By the reaction of compound (I) or its alkali metal salt with compound(II) or its alkali metal salt, an alkali metal salt of compound (III)will be formed. By subjecting the reaction solution containing thisalkali metal salt of compound (III) to acid treatment, compound (III)can be produced.

The acid may, for example, be a mineral acid such as hydrochloric acid,sulfuric acid or nitric acid, or an organic acid such asp-toluenesulfonic acid, and such an acid may be used as it is or in theform of an aqueous acid solution.

The acid is used in an amount sufficient to acidify the reactionmixture.

The temperature for the acid treatment is usually within a range of from0 to 100° C., preferably at most 60° C.

Compound (III) may be further purified by means of alkali and acidtreatment, extraction, washing, recrystallization or chromatography, asthe case requires.

Compound (III) obtained by the present invention, can be esterified withan alcohol, an alkyl halide or a dialkyl sulfate.

The esterification method may, for example, be a method wherein compound(III) is converted to an acid chloride or acid anhydride and thenreacted with an alcohol, a method wherein compound (III) is reacted withan alcohol in the presence of an acid catalyst such as sulfuric acid, amethod wherein compound (III) is reacted with an alcohol in the presenceof a dehydrating agent such as dicyclohexylcarbodiimide, a methodwherein compound (III) is reacted with various esterification agents, oran ester exchange reaction.

The esterification agents include, in addition to those mentioned above,a methanesulfonic acid ester produced from an alcohol andmethanesulfonyl chloride, a 4-toluenesulfonic acid ester produced froman alcohol and 4-toluenesulfonyl chloride, and a diazoalkane.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted to such specific Examples.

EXAMPLE 1

Into a reaction flask flushed with nitrogen, 59.7 g (0.3 mol) of2,6-dichloroquinoxaline, 33.0 g (0.3 mol) of hydroquinone, 24.2 g (0.6mol) of sodium hydroxide, 120 g of toluene and 180 g ofN,N-dimethylformamide were charged, and the temperature was raised from40° C. to 80° C. to form a sodium salt of4-(6-chloro-2-quinoxalyloxy)phenol. Into a separate reaction flaskflushed with nitrogen, 35.8 g (0.33 mol) of L-2-chloropropionic acid(optical purity: 96%ee), 17.5 g (0.165 mol) of sodium carbonate and 240g of toluene were charged and reacted by a conventional method at 50° C.to obtain a reaction solution in which a sodium salt ofL-2-chloropropionic acid was formed. To this reaction mixture, thereaction mixture of the sodium salt of4-(6-chloro-2-quinoxalyloxy)phenol was added together with 120 g oftoluene. To this mixture, 3.6 g (0.09 mol) of sodium hydroxide wasadded, and the mixture was reacted for 4 hours while azeotropicallydehydrating it at 60° C. under reduced pressure. Then, while maintainingthe temperature at 60° C., 240 ml of water was added, and the toluenelayer was separated and removed. Then, the aqueous layer was againwashed with 240 ml of toluene. Again, 240 ml of toluene was addedthereto, and 35% hydrochloric acid was added to bring the pH to 3,followed by liquid separation. The obtained toluene layer wasquantitatively analyzed by high performance liquid chromatography toconfirm formation of 98.3 g (yield: 95%) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid. The opticalpurity was 96%ee.

EXAMPLE 2

Into a reaction flask flushed with nitrogen, 59.7 g (0.3 mol) of2,6-dichloroquinoxaline, 33.0 g (0.3 mol) of hydroquinone, 24.9 g (0.57mol) of sodium hydroxide and 300 g of N,N-dimethylformamide were chargedand reacted at 35° C. for 3 hours under reduced pressure (20 mmHg).Then, the temperature was gradually raised to 75° C., and the mixturewas reacted at that temperature for 3 hours under reduced pressure (70mmHg). Then, 180 g of N,N-dimethylformamide was distilled off, and 480 gof toluene was added thereto. Then, 21.6 g (0.54 mol) of sodiumhydroxide was added thereto, and 42.3 g (0.39 mol) ofL-2-chloropropionic acid (optical purity: 96%ee) was added dropwisethereto over a period of 1 hour at 50° C. After completion of thedropwise addition, the temperature was raised to 60° C., and the mixturewas reacted for 4 hours while azeotropically dehydrating it underreduced pressure. Then, while maintaining the temperature at 60° C., 240ml of water was added, whereupon the toluene layer was separated andremoved. The aqueous layer was washed with 240 ml of toluene. Then, tothe aqueous layer, 240 ml of toluene was added, and the aqueous layerwas adjusted to pH 3 with 35% hydrochloric acid. Then, the aqueous layerwas separated and removed. The obtained toluene layer was quantitativelyanalyzed by high performance liquid chromatography to confirm formationof 96.2 g (yield: 93%) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid. The opticalpurity was 96%ee.

EXAMPLE 3

27.4 g (0.100 mol) of 4-(6-chloro-2-quinoxalyloxy)phenol, 40 g ofN,N-dimethylformamide and 120 g of toluene were charged into a flask,and 9.0 g (0.23 mol) of sodium hydroxide was added thereto. The mixturewas reacted at 40° C. for 1 hour. Then, 14.2 g (0.12 mol) ofL-2-chloropropionic acid was added thereto at 50° C. Then, thetemperature was raised to 60° C., and the mixture was reacted for 4hours while azeotropically dehydrating it under reduced pressure. Then,while maintaining the temperature at 60° C., 80 ml of water was addedthereto, and the toluene layer was separated and removed. Then, theaqueous layer was further washed with 80 ml of toluene. To the aqueouslayer, 80 ml of toluene was added, and the aqueous layer was adjusted topH 3 with 35% hydrochloric acid. Then, the aqueous layer was separatedand removed. The obtained toluene layer was quantitatively analyzed byhigh performance liquid chromatography to confirm formation of 32.8 g(yield: 95%) of D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionicacid. The optical purity was 96%ee.

EXAMPLE 4

3.6 g of water, 2.64 g (0.014 mol) of tributylamine and 70.9 g (0.51mol) of potassium carbonate were added at 60° C. to a toluene solutioncontaining 98.3 g (0.29 mol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained inExample 1, and the mixture was stirred for 30 minutes. Then, 57.1 g(0.37 mol) of diethyl sulfate was added dropwise, and the mixture wasreacted for 5 hours. Then, 147 g of water was added thereto, and theaqueous layer was separated and removed. The toluene layer was washedtwice with 147 g of water and then the toluene layer was distilled toobtain 106.3 g (yield: 95%) of ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. The opticalpurity was 96%ee.

EXAMPLE 5

6.9 g (0.02 mol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, 15.9 g oftoluene and 4.64 g of N,N-dimethylformamide were charged into a flask,and the temperature was raised to 60° C. Then, 4.14 g (0.04 mol) ofthionyl chloride was added dropwise thereto at a temperature of from 60to 70° C. Then, the mixture was reacted at 70° C. for 4 hours to formD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid chloride.After cooling, excess thionyl chloride was distilled off under reducedpressure, and this reaction solution was added dropwise at a temperatureof not higher than 30° C. to a mixed liquid comprising 8.9 g (0.10 mol)of tetrahydrofurfuryl alcohol and 4.12 g (0.06 mol) of pyridine,followed by stirring at room temperature for 2 hours. Then, thisreaction solution was washed three times with a 1% sodium hydroxideaqueous solution and twice with 1% hydrochloric acid and then threetimes with water. Then, toluene was distilled off under reduced pressureto obtain 6.8 g (yield: 79%) of tetrahydrofurfurylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. The opticalpurity was 96%ee.

EXAMPLE 6

6.9 g (0.02 mol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, 15.9 g oftoluene and 4.64 g of N,N-dimethylformamide were charged into a flask,and 4.14 g (0.04 mol) of thionyl chloride was added dropwise thereto at40° C. Then, the temperature was raised, and the mixture was reacted at60° C. for 3 hours to formD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid chloride.After cooling, excess thionyl chloride was distilled off under reducedpressure. This reaction solution was added dropwise at a temperature ofnot higher than 30° C. to a mixed liquid comprising 11.7 g (0.10 mol) ofisopropylidene aminoxyethanol and 4.12 g (0.06 mol) of pyridine,followed by stirring at room temperature for 2 hours. Then, thisreaction solution was washed three times with a 1% sodium hydroxideaqueous solution, twice with 1% hydrochloric acid and then three timeswith water. Then, toluene was distilled off under reduced pressure toobtain 6.8 g (yield: 77%) of isopropylidene aminoxyethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. The opticalpurity was 96%ee.

EXAMPLE 7

3.5 g (0.01 mol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid and 8.8 g ofN,N-dimethylformamide were charged into a flask and stirred at roomtemperature. Then, 1.1 g (0.08 mol) of potassium carbonate and 1.3 g(0.011 mol) of tetrahydrofurfuryl chloride were added thereto. Thetemperature was raised to 110° C., and the mixture was reacted for 15hours to obtain 2.92 g (yield: 67%) of tetrahydrofurfurylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. The opticalpurity was 96%ee.

EXAMPLE 8

0.26 g of tributylamine and 12.0 g (87 mmol) of potassium carbonate wereadded at 60° C. to a toluene solution containing 9.83 g (29 mmol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained inthe same manner as in Example 1, followed by stirring for 30 minutes.Then, 14.9 g (58 mmol) of tetrahydrofurfuryl 4-toluenesulfonate wasadded dropwise thereto, and the mixture was reacted at 100° C. for 5hours. After cooling, 15 g of water was added thereto, and the aqueouslayer was separated and removed. The toluene layer was washed twice with15 g of water. Then, the toluene layer was distilled, and the residuewas crystallized from a solvent mixture of heptane-isopropyl ether toobtain 11 g (yield: 88%) of tetrahydrofurfurylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. The opticalpurity was 96%ee.

EXAMPLE 9

6.9 g (0.02 mol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, 15.9 g oftoluene and 4.64 g of N,N-dimethylformamide were charged into a flask,and the temperature was raised to 60° C. To this reaction solution, 8.3g (0.06 mol) of potassium carbonate and 0.5 ml of tri-n-butylamine werefurther added, and 7.2 g (0.04 mol) of tetrahydrofurfuryl2-methanesulfonate was added dropwise thereto at 60° C., followed bystirring for 2 hours. Then, the temperature was raised, and the mixturewas stirred at 80° C. for 14 hours. After cooling, the reaction solutionwas washed three times with water. Then, toluene was distilled off underreduced pressure to obtain tetrahydrofurfurylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. The opticalpurity was 96%ee.

EXAMPLE 10

6.9 g (0.02 mol) ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid and 15.9 g ofN,N-dimethylformamide were charged into a flask, and the temperature wasraised to 60° C. To this reaction solution, 8.3 g (0.06 mol) ofpotassium carbonate and 0.5 ml of tri-n-butylamine were added, andfurther 10.9 g (0.04 mol) of isopropylidene aminoxyethyl2-p-toluenesulfonate was added dropwise thereto at 60° C. Then, thetemperature was raised and the mixture was stirred at 80° C. for 4hours. After completion of the reaction, N,N-dimethylformamide wasdistilled off under reduced pressure, and toluene was added thereto.This reaction solution was washed three times with water. Then, toluenewas distilled off under reduced pressure to obtain isopropylideneaminoxyethyl D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. Theoptical purity was 96%ee.

According to the present invention,D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid and its estercan be produced at a high conversion in good yield without deteriorationof the optical purity.

What is claimed is:
 1. A process for producingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, whichcomprises reacting an alkali metal salt of4-(6-chloro-2-quinoxalyloxy)phenol with an alkali metal salt ofL-2-chloropropionic acid in an aromatic hydrocarbon solvent in thepresence of an aprotic polar solvent to obtain an alkali metal salt ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, and treatingit with an acid.
 2. A process for producingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, whichcomprises reacting an alkali metal salt of4-(6-chloro-2-quinoxalyloxy)phenol with L-2-chloropropionic acid in anaromatic hydrocarbon solvent in the presence of an aprotic polar solventand an alkali metal hydroxide to obtain an alkali metal salt ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, and treatingit with an acid.
 3. A process for producingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, whichcomprises reacting 4-(6-chloro-2-quinoxalyloxy)phenol with an alkalimetal salt of L-2-chloropropionic acid in an aromatic hydrocarbonsolvent in the presence of an aprotic polar solvent and an alkali metalhydroxide to obtain an alkali metal salt ofD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid, and treatingit with an acid.
 4. The process according to claim 1, wherein the alkalimetal salt of 4-(6-chloro-2-quinoxalyloxy)phenol is produced by reacting2,6-dichloroquinoxaline with hydroquinone in an aromatic hydrocarbonsolvent in the presence of an alkali metal hydroxide and an aproticpolar solvent.
 5. The process according to any one of claim 1, whereinN,N-dimethylformamide is used as the aprotic polar solvent.
 6. Theprocess according to any one of claim 1, wherein toluene or benzene isused as the aromatic hydrocarbon solvent.
 7. The process according toclaim 2, wherein the reaction is carried out while removing formedwater.
 8. A process which comprises the following steps:(a) reacting analkali metal salt of 4-(6-chloro-2-quinoxalyloxy)phenol with an alkalimetal salt of L-2-chloropropionic acid in an aromatic hydrocarbonsolvent in the presence of an aprotic polar solvent; or reacting analkali metal salt of 4-(6-chloro-2-quinoxalyloxy)phenol withL-2-chloropropionic acid in an aromatic hydrocarbon solvent in thepresence of an aprotic polar solvent and an alkali metal hydroxide; orreacting 4-(6-chloro-2-quinoxalyloxy)phenol with an alkali metal salt ofL-2-chloropropionic acid in an aromatic hydrocarbon solvent in thepresence of an aprotic polar solvent and an alkali metal hydroxide; (b)treating the product from step (a) with an acid to obtainD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid; and (c)esterifying the acid from step (b) to obtain ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate ortetrahydrofurfurylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate or isopropylideneaminoxyethyl D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate. 9.The process according to claim 8, wherein tributylamine is used as thetertiary amine.
 10. A process for producing ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate which comprisesesterifying D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidobtained by the process of claim
 1. 11. A process for producing ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidobtained by the process of claim 1, with diethyl sulfate in the presenceof a tertiary amine and a base.
 12. A process for producingtetrahydrofurfuryl D(+)-2-[4(6-chloro-2-quinoxalyloxy)phenoxy]propionatewhich comprises esterifyingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained bythe process of claim
 1. 13. A process for producing isopropylideneaminoxyethyl D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionatewhich comprises D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionicacid obtained by the process of claim
 1. 14. The process according toclaim 2, wherein the alkali metal salt of4-(6-chloro-2-quinoxalyloxy)phenol is produced by reacting2,6-dichloroquinoxaline with hydroquinone in an aromatic hydrocarbonsolvent in the presence of an alkali metal hydroxide and an aproticpolar solvent.
 15. The process according to claim 2, whereinN,N-dimethylformamide is used as the aprotic polar solvent.
 16. Theprocess according to claim 3, wherein N,N-dimethylformamide is used asthe aprotic polar solvent.
 17. The process according to claim 2, whereintoluene or benzene is used as the aromatic hydrocarbon solvent.
 18. Theprocess according to claim 3, wherein toluene or benzene is used as thearomatic hydrocarbon solvent.
 19. The process according to claim 3,wherein the reaction is carried out while removing formed water.
 20. Aprocess for producing ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate which comprisesesterifying D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidobtained by the process of claim
 2. 21. A process for producing ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidobtained by the process of claim 2, with diethyl sulfate in the presenceof a tertiary amine and a base.
 22. A process for producingtetrahydrofurfuryl D(+)-2-[4(6-chloro-2-quinoxalyloxy)phenoxy]propionatewhich comprises esterifyingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained bythe process of claim
 2. 23. A process for producing isopropylideneaminoxyethyl D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionatewhich comprises esterifyingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained bythe process of claim
 2. 24. A process for producing ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate which comprisesesterifying D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidobtained by the process of claim
 3. 25. A process for producing ethylD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionate, which comprisesreacting D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acidobtained by the process of claim 3, with diethyl sulfate in the presenceof a tertiary amine and a base.
 26. A process for producingtetrahydrofurfuryl D(+)-2-[4(6-chloro-2-quinoxalyloxy)phenoxy]propionatewhich comprises esterifyingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained bythe process of claim
 3. 27. A process for producing isopropylideneaminoxyethyl D(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionatewhich comprises esterifyingD(+)-2-[4-(6-chloro-2-quinoxalyloxy)phenoxy]propionic acid obtained bythe process of claim 3.